The present invention relates to textile substrates having yarn or threads provided with variable twist in accordance with a desired pattern, and methods and apparatus for making such textile substrates.
U.S. Pat. No. 5,706,642 to Haselwander relates to a process and system for forming a twisted yarn having multiple plies of yarn which eliminates the need for changing gears, cams, or other mechanical or manual devices and which permits large twist pattern variations in the product such that the length of the segments of a desired twist level may be varied along with the twist level. This yarn can be utilized for forming carpet or other textiles with unique and different patterns and aesthetics. The '642 patent accomplishes this system for forming a twisted yarn by using a motor controlled by a programmable controller which drives the respective motor at precise speeds for precise times to change the speed ratios in accordance with the pattern desired. As discussed in the '642 patent, the pattern achieved by this variable twist level is generally a pattern having a high variation of twist levels, ranging from 1.5 turns of twist per inch to 6.5 turns of twist per inch and the like. Thus, the carpet made by this process generally has twist levels in this entire range. When a textile substrate is formed using this high level of variable twists, as indicated in the '642 patent, different patterns can be achieved on the surface of the textile substrate. Thus, the purpose of the '642 patent is to cause variations in the twist levels such that different patterns are created and such that the variable twist levels can be easily programmed and varied.
As discussed in detail below, unlike the '642 patent, the present invention relates to using a very low variable twist level such that the overall pattern on the textile substrate is visually the same. By using a low variable twist level, as discussed in detail below, variations in the color from yarn lot to yarn lot, as well as other characteristics that may vary from manufacture runs, can be minimized, if not avoided, by using a low variable twist level such that these variations are not visually apparent to a person. Thus, the present invention uses a variable twist in essentially the opposite manner intended in the '642 patent.
In forming textile substrates, yarn is used wherein the yarn during manufacture runs is supplied from various yarn lots or spindles. The yarn generally is colored yarn and many times is colored by a dyeing process. The color of the yarn from lot to lot or spindle to spindle can, unfortunately, vary in color or other characteristics such that when a textile substrate is formed (in other words, the yarn is tufted into the primary backing), variations in the color of the yarn from spindle to spindle can be seen occasionally, and when this occurs, there is a clear demarcation between the spindle changes such that streaking occurs in the carpet substrate. Needless to say, when this occurs, a portion of the product is unusable and must be rejected and considered waste. This occurrence can lead to undesirable waste and costs to the carpet manufacturer. While efforts have been made to ensure that yarn lots are consistent, it is an imprecise science, and any slight color variation from spindle to spindle can, unfortunately, be seen by the observer using the carpet. When twisted yarn is used to make a carpet, this problem can be even more readily apparent. Accordingly, there is a desire in the industry to avoid streaking and to provide some type of process which can compensate for this color variation from yarn lot to yarn lot and other variations that may occur in the yarn from lot to lot.
In the art of twisting yarn and thread, hereinafter together referred to as yarn twisting, a pre-determined twist level and twist direction is selected and remains constant for a particular finished yarn. Twist level is defined as the turns of twist or wrap of the yarn or thread about each other for a given segment of length of the twisted yarn or thread. The twisting of yarn involves twisting at least one strand or ply of yarn together or about another such that there is a pre-determined number of turns of yarn twisted with or wrapped about another yarn. Various twisting techniques are utilized in the art to obtain a twisted multiple ply yarn product. For example, ring twisting wherein strands of yarn pass through a ring and are twisted as the ring rotates about a rotating bobbin on which the yarn is wound; two-for-one twisting wherein two bobbins of yarn are combined within a common can, and the yarns are passed through the center of a rotating yarn twister spindle and out a radial hole; and cabling wherein one or more yarn strands enter the bottom of a rotating twister spindle at the center and exit through a radial hole and enter an eyelet or ring to form a balloon which throws out about a supply bobbin of another yarn with which it is twisted; are three such methods for twisting yarn strands together or one or more yarns twisted about another yarn. In each method it is the general practice to maintain the twist level or number of turns per inch of the yarn constant. Machines that perform these methods include a common drive motor, and the ratio between the yarn speed and the final yarn package speed, which determines the twist level, is obtained by the use of change twist gears. Thus, the twist level of a particular yarn is constant and is monitored to remain constant. In order to change twist level, different change twist gears are utilized, but this can only be done for one twisted yarn at a time, i.e., a single yarn has only one twist level.
It has been found that if the twist level of a given yarn may be varied along its length, products made from such yarn, such as carpet, may have unusual aesthetic styling. In the prior art, an attempt to obtain twist variation along the length of the yarn was proposed in Lloyd (U.S. Pat. No. 2,933,881), which utilizes a variable speed device wherein the output speed is controlled by a control lever either moved by a cam or manually moved to change the speed of the yarn take-up spool to vary the twist of the yarn within the final package. It clearly is impracticable to vary the twist manually with such an apparatus since reproducible results would not be obtainable. If a cam is used to create the twist level variation, the variation is limited by the shape and size of the cam, and if another pattern of twisting levels is desired, the cam must be changed.
Yamada et al. (U.S. Pat. No. 4,569,192) involves single strand spun yarns wherein the fibers are spun, drafted and twisted. It was proposed to vary the twist and drafting of the strand while the spun yarn strand is being formed in yarn spinning equipment.
Furthermore, there is no known textile substrate, whether incorporated into carpet tiles or into rolls of carpet, wherein the amount of, and/or variation in, twist level of the yarns is provided to achieve a desired uniform appearance of the carpet in spite of possible variations in characteristics of the yarn provided from different supply spindles or caused by other reasons.